Giving Sunday the best build in Honkai: Star Rail can significantly improve his performance as a support unit in various team comps, especially those that have DPS units capable of summoning extra allies onto the field. Sunday is a 5-star Imaginary character who follows the Path of the Harmony, which makes him a support unit capable of buffing his teammates. Following a series of long leaks that detailed his design and then his alleged gameplay kit, HoYoverse confirmed Sunday as one of the new characters in Honkai: Star Rail 2.7, alongside Fugue, the 5-star version of Tingyun.

https://screenrant.com/honkai-star-rail-sunday-builds-team-comps-relics/